@BOOK{johnson,
title = {A handbook of active filters},
author = {D. Johnson and J. Johnson and H. Moore},
publisher = {Prentice-Hall, Inc,
Engewood Cliffs},
city = {N.J.07632, USA},
year = {1980}
}

@book{dfd_handbook,
 author = {Rorabaugh, C. Britton},
 title = {Digital Filter Designer's Handbook: Featuring C Routines},
 year = {1992},
 isbn = {0079111661},
 publisher = {McGraw-Hill, Inc.},
 address = {New York, NY, USA},
}

@book{Moschytz,
 author = {Moschytz, George S. and Horn, Paul},
 title = {Active Filter Design Handbook},
 year = {1981},
 isbn = {0471278505},
 publisher = {John Wiley \& Sons, Inc.},
 address = {New York, NY, USA},
} 

@book{Tiet02,
Title = {Halbleiter - Schaltungstechnik. Neuer Teil: Nachrichtentechnische 
Schaltungen},
Author = {Ulrich Tietze and Christoph Schenk and Eberhard Gamm},
Year = {2002},
Isbn = {3-540-42849-6},
Address = {Berlin},
Publisher = {Springer},
Edition = {12. Auflage}
}

@book{Horowitz,
 author = {Horowitz, P. and Hill, W.},
 title = {The Art of Electronics},
 year = {1989},
 isbn = {0-521-37095-7},
 publisher = {Cambridge University Press},
 address = {New York, NY, USA},
} 

@book{Hamming,
      author        = {Hamming, Richard Wesley},
      title         = {Digital filters; 1st ed.},
      publisher     = {Prentice-Hall},
      address       = {Englewood Cliffs, NJ},
      series        = {Prentice-Hall signal processing},
      year          = {1977},
}

@ELECTRONIC{lfilt,
author={Mark Biegert},
title={The Papoulis Filter (aka Optimum "L" Filter)},
url={http://mathscinotes.com/2011/06/the-papoulis-filter-aka-optimum-l-filter/}
}